Many spray foam kits are targeted for the ‘do it yourself’ crowd, but if you do it yourself and you encounter problems, be prepared to remove bad foam.
The good news
Foam is great in spots where nothing else will work quite as well. We used foam primarily for air sealing in odd spots, but also for insulation value in areas where it was difficult to blow cellulose. See our previous post on this topic, “Foam continued…“.
The bad news
Foam can be fussy. Foam itself must be within a specified temperature range, the surface must be clean and within a specified temperature range, the hose and gun must be in perfect working order, and once you start spraying you can’t stop for more then a few seconds without gumming up the spray gun. In addition, you must provide adequate ventilation and wear protective clothing, breathing gear and goggles. Does this sound like a DIY project? I’m guessing most applications of spray foam are successful. We had used about 6 kits before we ran into problems, but sometimes things go wrong.
In our case, since we are not professional installers we were not immediately aware that something was going wrong. The foam did not appear to be expanding as usual or curing properly. It looked a little more yellow than white and felt rubbery when poked. By the time we realized something was not right, we had sprayed some 40 linear feet of band joist area in the basement. We’re still not sure what caused the problem. Was it a bum kit or bad hose and gun? We had followed all the same precautions as before, but we had very different results.
At first the manufacturer told us to just let it air out, it would cure on its own, it just might take longer than usual. So we vented and waited a month. All we had was a sticky smelly mess.
After several conversations with the manufacturer, we were faced with two options. A. Remove the bad foam. B. Spray over it with a (hopefully) good layer of foam to seal in the bad smelly stuff. We decided to remove the foam. For more background on why we chose to remove the foam, see Martin Holladay’s post on GreenBuildingAdvisor, “Spray Foam Jobs With Lingering Odor Problems“.
Removing bad foam is a nasty job. In our case, removing foam from a roughly two foot deep cavity at the rim joist area around 12 inch deep trusses with sharp metal plates. Not an easy job. My arms ached and even though I wore a mask and ventilated the space I still woke up with headaches the next day.
When I started pulling out the foam, I realized there were several areas where the foam had shrunken away from the sheathing by as much as an inch. I’m a bit concerned about this. Was this just due to the bad foam, or had this happened in other areas?
I tried to remove as much of the bad foam as I could, but there were areas at the corners where I couldn’t reach and areas behind ducts and wires that I didn’t want to be poking around with the serrated knife I was using to cut the foam into sections for easier removal.
I was able to remove roughly 80% of the bad foam. For the remaining areas, we just foamed over them.
Mostly happy ending
So far, our re-foaming efforts have been positive. The replacement foam kit provided free by the manufacturer yielded nice expanding foam that cured normally. We’re not quite finished, but I’m keeping my fingers crossed that we won’t encounter any more problems. I’m also hoping that we don’t encounter any more smelly issues when the temperatures begin to rise next summer.